as to information, http://en.wikipedia.org/wiki/Space_x
$4490-12000/kg. This is for a rocket with ONE proven orbital insertion.
WI: Mankind had taken Space Exploration seriously
- Thread starter Antipater
- Start date
as to information, http://en.wikipedia.org/wiki/Space_x
$4490-12000/kg. This is for a rocket with ONE proven orbital insertion.
I was talking about the satellites. Seems unlikely DirecTV (for instance) is going to tell you how much any of its satellites cost.
I'd disagree pretty sharply with that. Given the technologies currently available to us, human exploration of space is a deeply stupid idea.
Um. We could perfectly well have put video cameras on Spirit, Opportunity or Phoenix. Phoenix' solar panels peaked at around 150 watts, and even towards the end they were still producing over 80 watts. More than enough power for video.
But video of what? The wind blowing dust across Mars' plains? -- No, given the weight and power limitations, adding video would have meant skimping on some other instrument or capability. Not worth it.
Let's see. Huygens, the Titan lander, massed 319 kg. Let's say [handwave] that our hypothetical Super Space Program could send a Super Huygens massing 10x that -- 3.2 tons. We'll say 200kg of this is our sampling robot, and the rest is the return vehicle: 3 tons of rocket.
Titan's escape velocity is about 2.6 km/s, and then Delta-V to Earth on a Hohmann minimum velocity transfer orbit is almost exactly 80 km/s. (Though it will take you something like 12 years. You can improve this a lot with a Jupiter flyby, but you have to wait for the right window, which can take years.)
Let's give our retrieval vehicle a magic rocket drive with a specific impulse of -- oh, say 1000 seconds, which is roughly equivalent to an exhaust velocity of 10 km/s. That's considerably better than any chemical rocket we've yet built, but hey -- this is the cool alternate timeline where people have been shoveling money into space.
Rocket equation is
83 k/s = 10 k/s * ln 3000 kg/final mass
8.3 = ln 3000kg / final mass
works out to about 1/4000, or a 750g return, including sample container. Bigger than I expected, actually.
-- To be fair, if I were designing this thing I'd build it in stages -- a chemical rocket to get it off Titan, then an ion drive with a crazy high Isp to bring it home. Improve the mass ratio a lot, at the price of making everything way more complicated and expensive. Also, those delta V figures are to Earth's surface, but don't include the delta V gain from aerobraking.
The point remains: with a POD in the 1960s, no, we would not be planning a Titan Sample Return today. To make that plausible would require either significant infrastructure in space, technologies we don't have yet, or crazyass bucketloads of money.
By definition, an unmanned probe is going to burn less fuel and be able to bring back more. The further you go from Earth, the worse this comparison becomes.
We haven't brought a lot of samples back because we haven't seriously tried. But if we really wanted to, we could have been bringing Moon rocks back by the ton a couple of decades ago. We didn't do it because there was more interesting stuff to be done.
You say this like it's a bad thing.
Seriously: if we're talking space /exploration/ -- which is the title of the thread, yes? -- then it's really hard to argue that it could have been done better with manned expeditions.
More money? Sure -- we could have had a balloons in the atmospheres of Jupiter and Venus by now, a lander on Europa, rovers sniffing around the polar regions of the Moon. That would have been awesome.
But they'd all still be unmanned, because that's just much much more efficient.
Doug M.
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Let's see. Huygens, the Titan lander, massed 319 kg. Let's say [handwave] that our hypothetical Super Space Program could send a Super Huygens massing 10x that -- 3.2 tons. We'll say 200kg of this is our sampling robot, and the rest is the return vehicle: 3 tons of rocket.
Titan's escape velocity is about 2.6 km/s, and then Delta-V to Earth on a Hohmann minimum velocity transfer orbit is almost exactly 80 km/s. (Though it will take you something like 12 years. You can improve this a lot with a Jupiter flyby, but you have to wait for the right window, which can take years.)
Let's give our retrieval vehicle a magic rocket drive with a specific impulse of -- oh, say 800 seconds, which is roughly equivalent to an exhaust velocity of 8 km/s. That's considerably better than any chemical rocket we've yet built, but hey -- this is the cool alternate timeline where people have been shoveling money into space.
Rocket equation is
53 k/s = 8 k/s * ln 3000 kg/final mass
6.62 = ln 3000kg / final mass
works out to about 1/750, or a 4kg return, including sample container. Bigger than I expected, actually.
-- To be fair, if I were designing this thing I'd build it in stages -- a chemical rocket to get it off Titan, then an ion drive with a crazy high Isp to bring it home. Improve the mass ratio a lot, at the price of making everything way more complicated and expensive.
The point remains: with a POD in the 1960s, no, we would not be planning a Titan Sample Return today. To make that plausible would require either significant infrastructure in space, technologies we don't have yet, or crazyass bucketloads of money.
An 8 km/s exhaust velocity is physically impossible for a chemical engine; the maximum you can get is around 450-500, and that with hydrolox or more exotic (and hence difficult to work with) propellants, and while you could get there easily with a solid-core nuclear rocket, those have their own problems. Titan does have the advantage that there's an awful lot of basically rocket fuel on the surface and in the atmosphere, though, so you could use an ISRU approach, and you neglect the Oberth effect (which is going to be extremely useful for such a mission, given the high required delta-Vs).
Anyways, the whole point of what they've been saying is that with greater investment we would have (to a certain extent) significant infrastructure, more advanced technology, and, if not precisely crazyass bucketloads than much more cash to be spent on space. I tend to agree with them to a certain extent; at the very least, we could have flown more probes, as you say, and have real space tourism (at least to the SpaceShipTwo level) and such by now. No O'Neillian space colonies or giant solar arrays, however, I'm afraid.
Doug M. said:
Actually, there are a couple problems with robotic sample retrieval. First of all, exactly because you can burn less they tend to be built to use way less. A human return vehicle has to weigh a whole bunch to get the crew up, so a couple tens of kilograms of samples are a comparatively minor influence in the system weight. A robotic return vehicle, OTOH, is sized exactly to fit the amount carried back, so reducing the amount of mass carried back will reduce the mass more than you might naively think, and so greatly reduce the cost and complexity of the mission. Essentially, people think Saturn V when you mentioned crewed flights, and Protons when you mention robotic flights.
Second, sample retrieval has historically been a problem, compared to human hands and human-controlled machines as far as just grabbing rocks or picking up a bit of regolith or drilling a core. Third, you're right that we haven't really tried, but it's not because "there was more interesting stuff to be done" so much as there was not-already-done stuff to be done. Space scientists find it much easier to justify their budgets if they're doing something no one has done yet rather than repeating the previous mission (but better!). And budgets are always and forever the name of the game...
Yes, because I believe that the final purpose of space exploration is the conquest and colonization of space. If you're not going to send people out eventually, why bother?
And manned missions can certainly do better science than robots can. Consider the Mars Exploration Rover Spirit. In its mobile service, Spirit logged 7.73 kilometers. Assuming that it studied everything within a 0.5 meter diameter of its undercarriage (given the limitations of the arm, that sounds about right), this adds up to a grand total of 3,865 square meters. To put that in perspective, that's a little less than the area enclosed by a running track at a local High School. And it took 6 years to do that.
According to the very scientists who worked on Spirit (source: Steven Squyres, PhD Planetary Science, Cornell University, who worked on the Mars Exploration Rovers, Mars Reconnaissance Orbiter, and is now working on the Mars Science Laboratory), two humans with a bag of geology tools could do all of what Spirit achieved in the course of a week. Multiply this by 18 months (surface stay on Mars before the earth return window opens up), and you get the figure of two humans achieving basically the entire exploration record of Spirit 72 times over. Multiply this further, as most manned Mars plans feature 4-6 person crews, and you get a human mission that can, conservatively, do the equivalent of 144 Mars Exploration Rover missions, in the course of 18 months.
Now, let's do this by cost. Granted, a humans-to-Mars mission will be more expensive. But just how much more? The entire Spirit-Opportunity MER program cost about $950 Billion, extensions and all. Assuming that a single human mission, like the one described above, would cost, say, 72 times that amount (2 rovers achieve twice the exploration of one, so the human mission's advantage is reduced to 72 times the area explored) is not unreasonable, but it is still well in excess of what the US government estimates an actual humans-to-Mars mission would cost. In 1992, the US Congress graded the NASA Design Reference Mission 3.0 (http://en.wikipedia.org/wiki/NASA_Design_Reference_Mission_3.0) at $55 billion for the whole development, and another $5 billion for each subsequent mission. At that rate, even the first human mission more than offsets in terms of exploration achieved the added costs.
Oh sure, you can argue that they wouldn't be doing such a productive Extra-Vehicular Activity every week. But the point stands that, after a few human missions, more science would have been done per dollar spent than an equal amount of funding to unmanned probes would have.
I did say 'magic'!
-- Actually, it would be sort of fun to design a Titan Sample Return mission.
Upon further research, it turns out that 319kg figure for Huygens included fuel; the landing mass of the descent module was about 200 kg. So, "ten Huygenses" would be ~2000 kg.
Other hand, you can get the mass ratio up to a not-insane ~~0.04 or so if you do a staged return (chemical/ion) and allow either aerobraking or capture in Earth orbit. Very roughly 80 kg, including return capsule mass. Not horrible.
(ISRU: it's true Titan's atmosphere has a lot of potential fuel. It's 90% inert nitrogen, though. I suspect you could probably design an engine to burn it anyway, but you'd probably want an in situ test first...)
You're right about the Oberth effect. But from where, though? Jupiter would be ideal, but even with an ion drive you're talking a window that's open maybe two years out of every 18. Either you time the mission just right, or -- more likely -- you end up having to trade mass ratio for mission length. And mission length would be an issue; even with an ion drive and a transfer, we're still talking minimum 15 years round trip.
Isn't this a bit like saying "if I ride my bicycle to the supermarket I can bring back one sack of potatoes, but if I drive an M1 Abrams battle tank I can bring back six"?
Doug M.
Indeed. If we're not going to send people to live on the bottom of the ocean, why bother with it?
Also, I think geoscience should stop researching the Earth's crust until we make a public commitment to building human habitats at least ten kilometers underground.
No offense, but at this point I started to giggle out loud.
The 1993 DRM was inspired by the 1990 first draft of Robert Zubrin's Mars Direct. I have a lot of respect for Zubrin, but you have to read him very carefully, and when it comes to time and cost estimates... well. Basically, we are always ten years away from men on Mars -- in 1990 it was "obviously" possible to do it by 1999 -- and it will never cost more than "what we spend on cosmetics and hair care products every year!"
NASA has done two more recent DRMs than that, 4.0 and 5.0. Neither involved cost estimates. There's a reason for that.
Note that the Curiosity mission to Mars was initially estimated at ~$900 million. By appropriations time that had grown to $1.63 billion. As of Sept. 30, the actual price tag was approaching $3 billion.
Doug M.
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BTW, the now-forgotten 1970s Soviet Lunar program did three sample return missions from the Moon. Payloads were in the 100 gram range, but that could easily have been scaled up.
The Soviets also put a couple of television cameras on the second rover. Didn't record anything too interesting, but they did it.
Doug M.
The Soviets also put a couple of television cameras on the second rover. Didn't record anything too interesting, but they did it.
Doug M.
The following Design Reference Missions were scaled up for no good reason. DRM 5.0 is the most obvious offender, using 4 Ares Vs and nuclear thermal rockets for a crew of merely 6 crew, with basically the same surface capabilities as DRM 3.0 would have provided for only 3 heavy lift rockets on chemical stages.
Also, I would like to hear your reason for rejecting my source. Just because a single unmanned mission under construction in a NASA that was stripping funds from pure science (Under Griffin) means that an entire flagship Humans-To-Mars mission would suffer the same?
Quick: name three major NASA missions from the last 20 years that have come in at or under the original cost estimates. I don't think it's possible.
(I think it might be possible to come up with three that have come in at or under the actual budget authorization, since the budget usually grows comfortably between initial cost estimate and the time it leaves Congress. I can think of one, so there might be two others. But it's not easy.)
It's not just Mars. New Horizons is about 30% over budget. The JWST, much the same. The cost overrun problems did get worse under Griffin, but they predate him by decades, and they don't seem to have improved much in the 20 months since he left.
You don't get to wave a wand and say "well, this program would somehow be magically immune to NASA's well-documented long-term tendency to massive cost overruns".
Doug M.
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As to DRM 3.0: they increased the mass because the mass of the original proposal was ludicrously light. It involved about 400 tons launched to orbit, with a payload to Mars surface of 40 tons.
By way of comparison, an empty 18-wheeler truck weighs about 16 tons (10 tons of tractor, 6 tons of trailer). So, 2.5 of those to keep the crew alive on Mars' surface for nearly two years -- power plant, shielding, life support, equipment, everything.
That's just barking mad, and subsequent studies quietly acknowledged this.
As to cost: the Curiosity rover works out to about $3.1 billion/ton. Phoenix, which was about 350 kg, cost about $450 million, or about $1.3 billion per ton. Given that Curiosity is mobile, and expected to last for years instead of a few weeks, those figures don't seem grossly out of whack.
So if you want to land something more complex than an immobile, throwaway probe on Mars surface, $3 billion per ton in 2010 dollars is probably a decent BOTE figure. (Getting it back off Mars is, of course, a separate question.)
Doug M.
By way of comparison, an empty 18-wheeler truck weighs about 16 tons (10 tons of tractor, 6 tons of trailer). So, 2.5 of those to keep the crew alive on Mars' surface for nearly two years -- power plant, shielding, life support, equipment, everything.
That's just barking mad, and subsequent studies quietly acknowledged this.
As to cost: the Curiosity rover works out to about $3.1 billion/ton. Phoenix, which was about 350 kg, cost about $450 million, or about $1.3 billion per ton. Given that Curiosity is mobile, and expected to last for years instead of a few weeks, those figures don't seem grossly out of whack.
So if you want to land something more complex than an immobile, throwaway probe on Mars surface, $3 billion per ton in 2010 dollars is probably a decent BOTE figure. (Getting it back off Mars is, of course, a separate question.)
Doug M.
Sure. Understand, I'm not saying it's impossible. Just dangerous -- who remembers Mars Observer, Beagle 2, or the Mars Polar Lander? -- difficult, and crazy expensive.
Let's say we could do a Mars landing and return for a payload to surface of 200 tons. I think that's optimistic, but let's go with it.
BOTE figure would be $600 billion -- 3/4 of an Iraq War.
Who's in?
Doug M.
Let's say we could do a Mars landing and return for a payload to surface of 200 tons. I think that's optimistic, but let's go with it.
BOTE figure would be $600 billion -- 3/4 of an Iraq War.
Who's in?
Doug M.
Those are exactly the kind of figures I had in mind when I started this thread. IF we had governments willing to spend that kind of money on space exploration, what could we have accomplished exploring (and ultimately exploiting) our solar system? The manned or unmanned exploration debate is not one I thought of at first. It seems pretty logical to me for unmanned probes to precede any sort of human exploration, but I'd like to think that humans will follow the probes eventually, once the engineering and technological hurdles have been cleared.
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I find your figure quite pessimistic. All you really need are the following:
20-25 tonne surface hab.
5-tonne Earth Reentry Capsule and another 20 tonnes for the rocket to push it off Mars. Fuel to be provided by ISRU.
25-30 tonne Earth Return Vehicle, to sit in Mars Orbit until the crew rendezvous with it in their capsule (launched off Mars) and launch back to earth.
The Hab and ERV have all the consumables needed for a 4-person crew during their respective stretches of the mission.
And your figure of $3 billion per tonne assumes that we'll be developing the payload from scratch. We won't. The idea is to use as much existing hardware as possible. That Reentry Capsule I mentioned? Doesn't need to be any more complex than an Apollo CM, for example. The surface hab would use technology already proven on the ISS (the urine recycler comes to mind). The nuclear reactor has already been studied by NASA and the USAF in the early 1990s. The ERV can be nothing more complex than the already-in-development Bigelow Aerospace BA 330 module. In fact, that one's probably bigger than our needs (certainly heavier).
Out of curiosity, where do you get your 200 tonne figure from? What could possibly weigh so much? Hab and ERV wouldn't weigh much more than 20 tonnes (more for Hab, less for ERV), with one of those left on orbit. Ascent Vehicle would weigh something similar. To me, that adds up to about 60 tonnes. Even if we were to add another fully-packed module with extra equipment, we'd only have 80 tonnes on or near Mars.
just a random aside (to throw my thoughts into this),
well i for one wish we had taken space exploration more seriously then we have. imagine what is out there for us to find. we are basically (for want of a bad analogy) coming out of the dark ages (us being europe), with the whole world to explore yet.
lol i just hope that in my life time there will be at least one mission to europa (unmaned of course), since it holds the best chance for life in the universe (as they are reasonably sure there is some liquid water under all that ice).
well i for one wish we had taken space exploration more seriously then we have. imagine what is out there for us to find. we are basically (for want of a bad analogy) coming out of the dark ages (us being europe), with the whole world to explore yet.
lol i just hope that in my life time there will be at least one mission to europa (unmaned of course), since it holds the best chance for life in the universe (as they are reasonably sure there is some liquid water under all that ice).
The main reason from what I see is NASA and all other space agency try to reesign the wheel. In the 60's 70' and early 80's this was need but when silcon valley toke off they should left design of the computer to them.
Granted if they had a buget even 1/15th that of DOD they would still be able to alot more.
To answer the guestion I will follow the idea NASA state at the Apollo funding levels.
The space would have in orber in 1979. A space Colony on the moon in the early 90s. Bussines would had started to mine on the moon by the late 90s. Metors and Asteroid mining start by the early 2000s and man trip to Mars would be under way right now. The number of probes to other planet in the inner solar system would be at least 3 time the current numbers. In the outer solar system therewould be two or three probles orbiting Jupiter and Saturn and one in proble in orbiting Uranus and Neptune. Ground work for a space station in orber around mars would be in the works and also in the works would be the first man mission outer side the inner solar system.
Granted if they had a buget even 1/15th that of DOD they would still be able to alot more.
To answer the guestion I will follow the idea NASA state at the Apollo funding levels.
The space would have in orber in 1979. A space Colony on the moon in the early 90s. Bussines would had started to mine on the moon by the late 90s. Metors and Asteroid mining start by the early 2000s and man trip to Mars would be under way right now. The number of probes to other planet in the inner solar system would be at least 3 time the current numbers. In the outer solar system therewould be two or three probles orbiting Jupiter and Saturn and one in proble in orbiting Uranus and Neptune. Ground work for a space station in orber around mars would be in the works and also in the works would be the first man mission outer side the inner solar system.
Well, Earth's atmosphere is about 70% nitrogen, and LAC engines have been a fairly popular and somewhat developed idea for the last 40 years or so (say, about a TRL of 4-5). It doesn't seem like it should be tooo complicated to put something together, although you'd definitely want to test it first, as you say.
Of course, if we're going with nuclear engines, it doesn't matter anyways, since you can burn that crap directly.
Saturn, obviously. Why would you go anywhere else when you're in orbit around the second most-massive planet in the Solar System?
Nah, it's more like "If I say my commute is 3 miles, work'll only pay for a bicycle that I can carry one bag of groceries on, but if I say I commute 10 miles, they'll give me an SUV that I can carry 10 in"
Doug M. said:
I do
But it's not quite so bad as you say, since Mars mission reliability has increased drastically since the "Goblin" days of the '60s and '70s. Since 1990, 9 out of 16 Mars missions were successful, and if you only look at missions launched since 2000--7 out of 8 (the sole failure being Beagle 2). If you look at just American missions, we're 7 for 11 since 1990, and 5 for 5 since 2000. The main reason we have such a low success rate for the pre-2000 period is the Climate Orbiter/MPL/Deep Space 2 screw-up, and I would hope a crewed spacecraft would be able to figure out that they were going to burn up; that should be one major advantage humans have over current robots, that we can notice when things aren't right.Doug M. said:
Sure as shooting I would be. It would be a hell of a lot more useful in the long run, and far more useful (in scientific terms) than most of the things that would be spent on instead (alas, not the NSF/NIH). Besides, the cost would almost certainly be spread over a decade or two, meaning that you wouldn't necessarily be spending more than around $60-30 billion annually on it, so you'd only have to double-quintuple NASA's current budget. Just cancel the F-35 and buy some new F-16s instead...
I was thinking of that when I talked about sample return. I doubt they could have easily been scaled up due to the limitations of the Soviet mission design (they wanted them to come back the Soviet Union, naturally enough, and they wanted a very simple return trajectory, which IIRC basically limited them to a few areas of the Moon), the limited capacity of the Proton, and the difficulty of collecting more samples (they couldn't launch a rover and a sample return on the same probe, and I don't think they'd have come up with some of the more insane sample return schemes that have been seen with Mars, if only because their automation technology sucked). Plus, those probes didn't have even a tenth of the ability of the Apollo astronauts (especially Harrison Schmitt, of course) to discriminate between and collect samples, since they had basically a fixed arm with a drill on it that could collect a sample from one point and one point only (rather like an even more limited version of the Viking probe), which point depended heavily on how exactly the probe touched down.
If anything, the whole exercise just goes to show how terrible automated sample return is.
We're not really sure how big a Mars habitat will have to be, but 25 tons is certainly much, much too small.
Two comparanda: the ISS (crew of 6) masses just under 400 tons. The old Amundsen-Scott dome at the South Pole (crew of 20) massed about 500 tons empty -- no food, people or fuel, and not including the weight of the construction equipment.
Doug M.